At various ports of entry, secure buildings, and other locations, the inspection of people, in addition to luggage and cargo, is becoming mandatory. In addition to cargo vehicles, contraband such as explosives, weapons, narcotics, dangerous chemicals, and nuclear and radioactive materials can also be concealed on a person's body for illegal transportation.
Following a report of an individual attempting to destroy a commercial aircraft in-flight by detonating explosives hidden in his shoes, passengers are required to remove their shoes for separate inspection by X-ray systems. The shoe divestiture process causes great inconvenience and delays at checkpoints. Whole body or shoe metal detectors can detect metallic weapons, but result in large false-alarm rate due to the common use of metallic shoe shanks.
Prior art systems for detecting objects concealed on persons do exist but are not adapted to effectively screen the shoes of passengers. For example, U.S. Pat. No. 5,181,234 (hereinafter, the “'234 patent”), assigned to the assignee of the present invention, and herein incorporated by reference in its entirety, describes “[a] pencil beam of X-rays is scanned over the surface of the body of a person being examined. X-rays that are scattered or reflected from the subject's body are detected by a detector. The signal produced by this scattered X-ray detector in then used to modulate an image display device to produce an image of the subject and any concealed objects carried by the subject. The detector assembly is constructed in a configuration to automatically and uniformly enhance the image edges of low atomic number (low Z) concealed objects to facilitate their detection. A storage means is provided by which previously acquired images can be compared with the present image for analyzing variances in similarities with the present image, and provides means for creating a generic representation of the body being examined while suppressing anatomical features of the subject to minimize invasion of the subject's privacy.”
In addition, U.S. Pat. No. 6,094,472 (hereinafter, the “'472 patent”), also assigned to the assignee of the present invention and incorporated herein by reference, describes a method for using an X-ray backscatter imaging system for searching a subject for concealed objects, “comprising the steps of: moving the subject within a passageway, the passageway having an entrance and an exit; initiating operation of at least one X-ray source upon entry of the subject into the passageway; producing a pencil beam of X-rays having a low dose directed toward a scanning area at a plurality of scanning positions within the passageway; scanning the pencil beam of X-rays over the scanning area; tracking said pencil beam of X-rays to each of said plurality of scanning positions, wherein the tracking is substantially coordinated with forward progress of the subject through the passageway; using a plurality of detectors, detecting X-rays that are backscattered from said pencil beam as a result of interacting with the subject when positioned at each scanning position of the plurality of scanning positions; and displaying a digitally represented image of the detected backscattered X-rays.”
Other references, including U.S. Pat. Nos. 7,826,589, 7,796,733, 7,110,493, and 6,665,373, which are hereby incorporated herein by reference, and technologies, including millimeter wave technologies, similarly do not teach an improved way of screening an individual's shoes. Therefore, there is a need for a rapid and low false alarm rate inspection system for scanning a person's shoes without the need for the person to remove their shoes.
What is also needed is an integrated whole body, metal and shoe scanner system that can distinguish shoe metal shanks from actual threat items.